Departments of Preventive Medicine and Biometrics and of Pediatrics, University of Colorado School of Medicine; and Children's Hospital,Denver, Colorado the Department of Epidemiology, School of Public Health, University of North Carolina Chapel Hill, North Carolina

Address correspondence and reprint requests to Dr. Richard Hamman, Department of Preventive Medicine and Biometrics, University of Colorado School of Medicine, Denver, CO 80262.

Abstract

The hypothesis that breast-feeding can provide protection against the development of insulindependent diabetes mellitus (IDDM) and would, therefore, be less common among subjects with IDDM was tested with a retrospective design. Cases (n = 268) were selected from the Colorado IDDM Registry and the Barbara Davis Center for Childhood Diabetes (Denver, CO). Two control groups were recruited, one from physicians' practices throughout Colorado (n = 291) and the second through random-digit dialing from the Denver area (n = 188). Cases were less likely to have been breast-fed than controls after adjustment for birth year, maternal age, maternal education, family income, race, and sex [adjusted odds ratio (OR) = 0.70; 95% confidence interval (Cl) = 0.50–0.97]. This finding was consistent for both control groups and by birth-year intervals. A greater decrease in risk of IDDM was seen among subjects who had been breast-fed to an older age (for breast-feeding duration of ≥12 mo, adjusted OR = 0.54, 95% Cl = 0.27–1.08). The amount of IDDM that might be explained by breast-feeding habits (population percentage attributable risk) ranged from 2 to 26%, varying according to the breast-feeding prevalence reported in other studies. Replication of this work in different populations, controlled for the strong secular trends in breast-feeding habits, is critical before the hypothesis of protection is accepted.